Conifer Takeover in the Sagebrush Sea

By dcronenwett January 28, 2019
UM Bird Ecology Lab Technician working near Dillon

When you picture the vast, wide-open sagebrush country what bird first comes to mind? You may picture a sage grouse: this unique bird is often the “poster species” for sagebrush habitat not only due to their striking displays, but also because they are a sagebrush obligate, requiring sagebrush habitat for survival.  Greater Sage Grouse have been in the media spotlight in recent years, due population declines associated with sagebrush removal and various kinds of development. A lesser-known cause for sagebrush loss is conifer encroachment: evergreen trees have expanded into open areas of sagebrush habitat, largely as a result of climate change and fire suppression.

If left unchecked, these conifers can transform open sagebrush into dense forest with little or no understory. Furthermore, scientists have found that breeding sage grouse are particularly sensitive to even a few trees in the landscape, and when trees are removed before sagebrush declines, the iconic sage grouse does benefit. But what about the 350+ other species that live in this ecosystem? Birds like Brewer’s Sparrow, White-crowned Sparrow, Green-tailed Towhee, Sage Thrasher, Vesper Sparrow, Western Meadowlark, and many others, are commonly found within sagebrush habitat in Montana. The effects of conifer removal for other species that reside in the sagebrush sea have largely gone unstudied.

What can songbirds tell us?

Sage grouse have received most of the research attention to date, yet they are not easily monitored because they have large territories and a complex life cycle. Songbirds are ideal indicators of habitat conditions since they are relatively abundant, highly visible, easily surveyed, and provide feedback from an entire community rather than a single species. “A trained birder can collect information from the entire bird community just by recording the birds they see and hear during in a short period of time”, says Anna Noson, a researcher with University of Montana Bird Ecology Lab.

Researchers at the Bird Ecology Lab and the Montana Cooperative Wildlife Research Unit are collaborating on a new study to learn how conifer management practices influence songbirds in sagebrush habitats in southwestern Montana. A few years into the study, the Bird Ecology Lab has measured little change in the sagebrush bird community following mechanical and prescribed fire treatments by the Bureau of Land Management (BLM).  However, bird abundance does not guarantee that the area is good for breeding.

“Removing conifers may make the sagebrush habitat attractive [to birds] for settling, but those individuals near remaining woody cover may have low nest success, meaning negative impacts on populations,” says Dr. Thomas Martin, a university professor with the Montana Cooperative Wildlife Research Unit. He goes on to explain, “Thicker conifer cover can serve as reservoirs of predators that target sagebrush nests.”

University of Montana researchers say coupling information on bird abundance with nesting success will allow a more thorough understanding of the impacts of conifer removal. Only then will we understand how these management practices are affecting species of the sagebrush sea.

*This research will be ongoing for the next few years and is performed collaboratively with the following partners: Bureau of Land Management, U.S. Fish and Wildlife Service, Montana Fish, Wildlife & Parks, The Nature Conservancy, Montana Cooperative Wildlife Research Unit and University of Montana Bird Ecology Lab. If you have specific questions regarding this study please contact Anna Noson, UM Bird Ecology Lab (anna.noson@mso.umt.edu).